assign a sector to an angle in R - r

Question

I have a vector of start and end angels values between 0 and 360.
I would like to have an additional column that specifies in which sector(consider 12 sectors) are my variables.
sectors should be defined as : (15:45], (45,75],(75,105], ..., (345,15]
test = structure(list(start = c(4, 67, 13, 35, 54, 0), end = c(23, 84,
30, 52, 71, 0)), row.names = 2:7, class = "data.frame")
For my test example I thought I have to loop over the number of rows :
for( i in 1:nrow(test)){
if(test$start[i] <= 15 | test$start[i] >345){test$sector_start[i] = 12}
else if(test$start[i] > 15 & test$start[i] <= 45){test$sector_start[i] = 1}
else if(test$start[i] > 45 & test$start[i] <= 75){test$sector_start[i] = 2}
else if(test$start[i] > 75 & test$start[i] <= 105){test$sector_start[i] = 3}
else if(test$start[i] > 105 & test$start[i] <= 135){test$sector_start[i] = 4}
else if(test$start[i] > 135 & test$start[i] <= 165){test$sector_start[i] = 5}
else if(test$start[i] > 165 & test$start[i] <= 195){test$sector_start[i] = 6}
else if(test$start[i] > 195 & test$start[i] <= 225){test$sector_start[i] = 7}
else if(test$start[i] > 225 & test$start[i] <= 255){test$sector_start[i] = 8}
else if(test$start[i] > 255 & test$start[i] <= 285){test$sector_start[i] = 9}
else if(test$start[i] > 285 & test$start[i] <= 315){test$sector_start[i] = 10}
else if(test$start[i] > 315 & test$start[i] <= 345){test$sector_start[i] = 11}
if(test$end[i] <= 15 | test$end[i] >345){test$sector_end[i] = 12}
else if(test$end[i] > 15 & test$end[i] <= 45){test$sector_end[i] = 1}
else if(test$end[i] > 45 & test$end[i] <= 75){test$sector_end[i] = 2}
else if(test$end[i] > 75 & test$end[i] <= 105){test$sector_end[i] = 3}
else if(test$end[i] > 105 & test$end[i] <= 135){test$sector_end[i] = 4}
else if(test$end[i] > 135 & test$end[i] <= 165){test$sector_end[i] = 5}
else if(test$end[i] > 165 & test$end[i] <= 195){test$sector_end[i] = 6}
else if(test$end[i] > 195 & test$end[i] <= 225){test$sector_end[i] = 7}
else if(test$end[i] > 225 & test$end[i] <= 255){test$sector_end[i] = 8}
else if(test$end[i] > 255 & test$end[i] <= 285){test$sector_end[i] = 9}
else if(test$end[i] > 285 & test$end[i] <= 315){test$sector_end[i] = 10}
else if(test$end[i] > 315 & test$end[i] <= 345){test$sector_end[i] = 11}
}
here I could add 2 column to test which is telling me my angles are in which sector. I'm looking for a smarter way of doing this that I could have an option to vary the number of sectors, for example to 24 sectors.

Answer 1

As Roman says, you can use cut. The last step is for angles > 345 or <= 15.
library(dplyr)
test %>%
mutate(sector_start = cut(start, 15 + 30*(0:11), 1:11)
, sector_end = cut(end, 15 + 30*(0:11), 1:11)) %>%
mutate_at(vars(contains('sector')), ~ifelse(is.na(.), 12, .))
In base R:
test[paste0('sector_', names(test))] <-
lapply(test, function(x){
labs <- cut(x, 15 + 30*(0:11), 1:11)
ifelse(is.na(labs), 12, labs)
})